Compensator for temperature-caused length change

ABSTRACT

An elongated structure whose effective length is substantially independent of changes in ambient temperature. The structure includes between its ends an elongated portion whose length varies directly with changes in ambient temperature operatively connected end-to-end to a plunger and cylinder assembly whose effective length varies inversely with changes in ambient temperature. Positive-temperature-coefficient fluid is provided in a chamber in the cylinder whereby expansion of this fluid shortens the assembly and contraction of the fluid lengthens the assembly.

United States Patent [72] Inventor CarlV.VonL1nsowe San Jose, Calif.[21] Appl. No. 8,842 [22] Filed Feb. 5, 1970 [45] Patented Jan.4, 1972[73] Assignee JohnT. Page Portland, Oreg. apart interest [54]COMPENSATOR FOR TEMPERATURE-CAUSED LENGTH CHANGE 6 Claims, 2 DrawingFigs.

[52] U.S.(l 137/344, 239/212 [51] lnt.(l BOSb 9/02, E0 1 h 3/02 [50]Field of Search 137/344; 239/212, 213, 397.5; 73/3682 [56] ReferencesCited UNITED STATES PATENTS 2,183,596 12/1939 Trinks 23 9/3975 p2,800,364 7/1957 Dick et al. 239/212 X 3,213,918 10/1965 Rudzki et al239/397.5 X 3,233,459 2/1966 Gleason et al. 73/3682 X 3,259,319 7/1966Wallace 239/212 X 3,282,103 11/1966 Steele.... 73/3682 X 3,365,9461/1968 Hall 73/3682 X 3,491,784 l/1970 Lilly 137/815 3,519,206 7/1970Leaders 239/213 Primary ExaminerSamuel Scott Attorney-Kolisch & HartwellABSTRACT: An elongated structure whose effective length is substantiallyindependent of changes in ambient temperature. The structure includesbetween its ends an elongated portion whose length varies directly withchanges in ambient temperature operatively connected end-to-end to aplunger and cylinder assembly whose effective length varies inverselywith changes in ambient temperature. Positive-temperature-coefficientfluid is provided in a chamber in the cylinder whereby expansion of thisfluid shortens the assembly and contraction of the fluid lengthens theassembly.

mama m 4 mrz ma V. mv awake BY KM q H ML COMPENSATOR FORTEMPERATURE-CAUSED LENGTH CHANGE BACKGROUND OF THE INVENTION Thisinvention pertains to length-change compensation. More particularly, itpertains to a compensator which may be incorporated with an elongatedmember whose length changes directly with changes in ambient temperatureto produce a structure having an overall length that is substantiallyindependent of ambient temperature. A preferred embodiment of theinvention is described herein in conjunction with parts in a mobileirrigator wherein it has been found to have particular utility.

There are many applications where it is desirable to use a structurewhose dimensions remain substantially constant despite changes inambient temperature. This is particularly important where a structurehas one or more relatively large dimensions (for example, length), andis interconnected with other structures. In such an assembly, atemperatureproduced dimension change in a structure might well result inoverstressing and damage to different parts in the assembly.

As an illustration, in a mobile irrigator having an elongatedarticulated multiple-section frame, with such supported at differentpoints for travel over the ground in a direction substantially normal tothe longitudinal axis of the frame, length-stability in the longitudinalstructures of the frame is a very important consideration. The frame insuch an irrigator might, for example, be as much as a quarter mile orso. With this the case, any substantial length changes that occur in theframes longitudinal structures may produce damaging side loading on theground-traveling supports provided for the frame.

SUMMARY OF THE INVENTION Therefore, a general object of the presentinvention is to provide a novel compensator which may be incorporatedwith an elongated member whose length changes directly with changes inambient temperature to produce a length-stable structure having anoverall length that is substantially independent of ambient temperature.

Another object of the invention is to provide such a compensator whichwhen incorporated in the type of structure mentioned, is capable oftransmitting an axial load.

Still a further object of the invention is to provide a compensator ofthe type generally indicated which is reliable and simple inconstruction, and which may readily be incorporated in many differenttypes of structures. 1

Thus, and according to a preferred embodiment of the invention, acompensator is proposed which takes the form of a cylinder and plungerassembly, wherein there is a chamber defined between the plunger andcylinder containing positivetemperature-coefficient liquid. With anincrease in ambient temperature, the liquid in the chamber expands, andshifts the plunger and cylinder relative to one another to shorten theoverall effective length of the assembly. The reverse action takes placewith a decrease in ambient temperature. The compensator is mountedsubstantially in longitudinal alignment with a structural member whoselength varies directly with changes in ambient temperature to produce anoverall structure whose length is substantially independent oftemperature.

The specific length change which occurs in the compensator for a giventemperature change depends upon the dimensions of the plunger and thecylinder. Thus, a compensator may be provided to take care of manydifferent types of situations.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and advantagesattained by the invention will become more fully apparent as thedescription which follows is read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a simplified front elevation illustrating portions of anelongated articulated mobile irrigator including longitudinal framestructures incorporating the present invention; and

FIG. 2 is an enlarged view illustrating a compensator constructedaccording to the invention mounted endo relative to a longitudinal trussin the irrigator of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION Turning now to the drawings, andreferring first to FIG. I, indicated generally at 10 is an elongatedarticulated mobile irrigator which extends a considerable distance overthe ground, shown at 12. The irrigator includes a multiple-section framemade up of two spaced substantially parallel rows of longitudinalstructures, such as the row shown in FIG. I containing longitudinalstructures 14. Extending transversely between the two rows oflongitudinal structures, between points adjacent different sets ofconfronting ends of the longitudinal structures, are transversestructures (not shown) which are similar in construction to thelongitudinal structures. Adjacent sets of ends of longitudinal andtransverse structures are interconnected through suitable articulationmeans, such as those indicated generally by circular outlines at 16,which accommodate a certain amount of relative angular movement betweenthe structures to take care of unevenness in the ground. Thelongitudinal and transverse structures in the frame are supported abovethe ground, and for movement thereover, through upright legs 18, andwheels 20 which are carried adjacent the lower ends of the legs.

In the irrigator illustrated, the longitudinal structures are about 120feet long. The transverse structures which are concealed behindarticulation means 16 are about 90 feet long. Legs 18 support thelongitudinal and transverse structures about l0 feet above the ground.The overall length of irrigator 10, indicated generally at A in FIG. I,is about one-quarter mile.

The irrigator is propelled over the ground, generally in a directionextending normally out of the plane of FIG. 1, by power drive meansincluding one or more traction units, such as traction unit 22, which iscarried adjacent the base of one of legs 18. The irrigator typicallytravels at a speed of about 1 mile per hour.

As will be more fully explained, each longitudinal structure in theframe of the irrigator includes an elongated rigid truss portion 24, anda compensator, or compensator means, 26. A compensator is mounted on anddisposed in substantially longitudinal alignment with its associatedtruss portion. The truss portions, or trusses, in the longitudinalstructures are employed to carry a suitable water-distribution systemincluding conventional sprinkler devices such as those shown at 28.

Referring now to FIG. 2, which shows in somewhat greater detail theconstruction of a longitudinal structure in the frame of the irrigator,truss 24 includes an elongated central framework represented by dash-dotblock 30. Joined to and extending axially from opposite ends of thecentral framework are hollow rectangular end members 32, 34. The centralframework in the truss is represented herein by a dash-dot block for thereason that details of its construction form no part of the invention,and may have any one of a number of different configurations. One typeof truss which may be used is described in detail in US Pat. No.3,562,994, issued to me on Feb. l6, I971, entitled Truss."

At a given ambient temperature, for example 70 F., truss 24 has a lengthmeasured between the outer ends of members 32, 34 indicated at T,. Onthe ambient temperature increasing to, say, F., the truss lengthens(through length changes in its parts) to a length indicated at T Theamount which the truss lengthens, of course, depends upon the sizes ofits parts, and upon the particular increase in ambient temperature whichoccurs. Similarly, the truss shortens with a decrease in ambienttemperature. Thus, the length of the truss changes directly with changesin ambient temperature.

To prevent such a temperature-produced length change from overstressingand damaging parts in the irrigators framework, compensator 26,constructed and mounted according to the invention, is provided. Ingeneral terms, compensator 26 comprises cylinder and plunger parts 36,38,

respectively. In the embodiment illustrated, cylinder 36 is formed froman elongated tube 40 provided with axially spaced ports 42 closed off byplugs 44 which are screwed into the ports. Joined to the left end oftube 40 in FIG. 2 is a circular plate 46 having a central bore 46a.Joined to the right face of plate 46 is a tubular collar 48. Fastened tothe right end of tube 40 is a circular plate 50 having a central bore50a.

The cylinder is secured to truss member 34 through a mounting plate 52.Plate 52 is suitably joined to plate 46, and includes a central bore52a, communicating with bore 46a. Lugs 56 joined to the left face ofplate 52 extend into member 34 as shown and are secured rigidly theretothrough fasteners 58. With such a mounting, he cylinder is disposed withits longitudinal axis substantially in line with the axis of truss 24,and is adapted tomove as a unit with the truss. I

Plunger 38 includes a rod 58 which extends slidably through bore 50a.The left end of the rod joins with a head 60 of larger outside diameterthan the rod. A recess 59 provided in the left end of head 60 in FIG. 2receives one end of a spring, or bias means, 62. The other end of thespring acts against the right face of plate 46, with collar 48 acting asa retainer for this end of the spring. Spring 62 is under compression,and tends to shift the plunger to the right in FIG. 2 relative to thecylinder. The outside of rod 58 is sealed to the inside of bore 50athrough a seal 64 which is mounted on plate 50. The outside of head 60is sealed to the inside of tube 40 through a 'seal 66 mounted on a ring68 which is suitably secured to the inside of tube 40 at the locationshown. The right end of rod 58 connects with an articulation means 16through a mounting plate 70.

'Indicated generally at 72 is a chamber defined between the cylinder andplunger which is entirely filled with a suitablepositive-temperature-coefficient liquid, such as methyl alcohol.

With an ambient temperature of about 70 F., the plunger and cylinderoccupy the relative positions shown therefor in solid outline in FIG. 2.With such the case, the organization including compensator 26 and plate52 has an effective length indicated at C,. On the ambient temperatureincreasing to about 85 F., the liquid in chamber 72 expands and actsagainst face 61 on head 60 to contract the compensator. In particular,with such a temperature increase, the compensator decreases in effectivelength an amount substantially equal to the increase in length resulting(from the same temperature increase) in truss 24. Thus, at the higherambient temperature mentioned, the length of the organization includingcompensator 26 and plate 52 is indicated at C curring in the ambienttemperature. In this case, the length of 1 the truss decreases and thelength compensator 26 increases (by substantially the same amounts). Theincrease in length in the compensator results from contraction of thefluid captured in chamber 72, and from the action of spring 62.

The invention thus provides novel means for providing an elongatedstructure whose length is substantially independent of changes intemperature. With a compensator such as compensator26 employed, axialloads may readily be transmitted therethrough. The size of such a loadis determined by the stiffness of the spring used corresponding tospring 62.

Ports 42 are used conveniently to provide access for filling chamber 72with fluid.

The invention offers a considerable advantage in an organization, suchas the frame in irrigator 10, where uncontrolled length changes in partsmight add up and cause severe internal overstressing and damage. Theparticular length change which occurs in a compensator due to a givenchange in ambient temperature is a matter of choice, depending upon therelative sizing of the parts in the plunger and cylinder.

While an embodiment of the invention has been described herein, it isappreciated that variations and modifications may be made withoutdeparting from the spirit of the invention.

Iclaim:

1. An elongated mobile instrumentality comprising at least a pair oflongitudinal structures disposed substantially end-to-end,

articulation means operatively interconnecting and permitting relativemovement between said structures,

and at least a pair of spaced-apart ground-traveling supports supportingsaid structures for movement over the ground to act on said parts in amanner producing relative movement therebetween which increases thedistance between said outer ends under all circumstances with atemperature decrease, and which decreases such distance under allcircumstances with a temperature increase; and

means operatively connecting said portion and said compensator meanssubstantially in longitudinal alignment, whereby on a change occurringin the ambient temperature, the resulting length change in saidcompensator means compensates for the resulting length change in saidportion, and the overall length of said structure remains substantiallyconstant.

2. In an elongated structure the combination comprising:

an elongated portion whose length changes directly with changes inambient temperature;

elongated compensator means including a pair of elongated relativelyreciprocable interconnected parts having spaced-apart relatively movableouter ends which are exposed, biasing means operatively interposedbetween and acting on said parts urging the same under all circumstancesto move relative to one another in a direction tending to increase thedistance between said outer ends, and means containing a captive body ofpositive-temperaturecoefiicient liquid, with such liquid held in aposition effective in a direction substantially normal to the structureslongitudinal axes,

said longitudinal structures each comprising between its ends anelongated portion whose length changes directly with changes in ambienttemperature, and elongated compensator means disposed substantially inlongitudinal alignment with said portion whose length changes inverselywith changes in ambient temperature in a manner whereby the overalllength of the structure remains substantially constant.

3. The structure of claim 2, wherein said bias means comprises a springunder compression.

4. The structure of claim 2, wherein one of said parts comprises acylinder, and the other part comprises a plunger slidably mounted onsaid cylinder.

5. The structure of claim 4, wherein said means containing said liquidcomprises a chamber defined between said cylinder and said plunger.

6. A length-change compensator for use in combination with an elongatedmember whose length changes directly with changes in ambienttemperatures to produce a structure having an overall length which issubstantially independent of temperatures comprising a pair of elongatedrelatively reciprocable interconnected parts having spaced-apartrelatively movable outer ends which are interposed,

biasing means operatively interposed between and acting on said partsurging the same under all circumstances to move relative to one anotherin a direction tending to increase the distance between said outer ends,and

means containing a captive body of positive-temperaturecoefficientliquid, with such liquid held in a position effective to act on saidparts in a manner producing relative movement therebetween whichincreases the distance between said outer ends under all circumstanceswith a temperature decrease, and which decreases such distance under allcircumstances with a temperature increase.

1. An elongated mobile instrumentality comprising at least a pair oflongitudinal structures disposed substantially end-to-end, articulationmeans operatively interconnecting and permitting relative movementbetween said structures, and at least a pair of spaced-apartground-traveling supports supporting said structures for movement overthe ground to act on said parts in a manner producing relative movementtherebetween which increases the distance between said outer ends underall circumstances with a temperature decrease, and which decreases suchdistance under all circumstances with a temperature increase; and meansoperatively connecting said portion and said compensator meanssubstantially in longitudinal alignment, whereby on a change occurringin the ambient temperature, the resulting length change in saidcompensator means compensates for the resulting length change in saidportion, and the overall length of said structure remains substantiallyconstant.
 2. In an elongated structure the combination comprising: anelongated portion whose length changes directly with changes in ambienttemperature; elongated compensator means including a pair of elongatedrelatively reciprocable interconnected parts having spaced-apartrelatively movable outer ends which are exposed, biasing meansoperatively interposed between and acting on said parts urging the sameunder all circumstances to move relative to one another in a directiontending to increase the distance between said outer ends, and meanscontaining a captive body of positive-temperature-coefficient liquid,with such liquid held in a position effective in a directionsubstantially normal to the structures'' longitudinal axes, saidlongitudinal structures each comprising between its ends an elongatedportion whose length changes directly with changes in ambienttemperature, and elongated compensator means disposed substantially inlongitudinal alignment with said portion whosE length changes inverselywith changes in ambient temperature in a manner whereby the overalllength of the structure remains substantially constant.
 3. The structureof claim 2, wherein said bias means comprises a spring undercompression.
 4. The structure of claim 2, wherein one of said partscomprises a cylinder, and the other part comprises a plunger slidablymounted on said cylinder.
 5. The structure of claim 4, wherein saidmeans containing said liquid comprises a chamber defined between saidcylinder and said plunger.
 6. A length-change compensator for use incombination with an elongated member whose length changes directly withchanges in ambient temperatures to produce a structure having an overalllength which is substantially independent of temperatures comprising apair of elongated relatively reciprocable interconnected parts havingspaced-apart relatively movable outer ends which are interposed, biasingmeans operatively interposed between and acting on said parts urging thesame under all circumstances to move relative to one another in adirection tending to increase the distance between said outer ends, andmeans containing a captive body of positive-temperature-coefficientliquid, with such liquid held in a position effective to act on saidparts in a manner producing relative movement therebetween whichincreases the distance between said outer ends under all circumstanceswith a temperature decrease, and which decreases such distance under allcircumstances with a temperature increase.